High electron emissive cathode



Patented Sept. 8, 1931 UNITED STATES PATENT OFFICE- RICHARD E. MIESSE, OF CHICAGO, ILLINOIS, A SSIGNOR TO Q. R. S. DE VRY CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS HIGH ELECTRON EMISSIVE CATHODE No Drawing.

My invention relates to a high electron emissive cathode and the process of making same.

In accordance with my inventionI have developed a'cathode of this character which shows a very high rate of electron emission as compared to other types as the thoriated tungsten emitter or the VVehnolt cathode.

My improved cathode is also better enabled to withstand positive ion bombardment. In the manufacture of my improved filament, I use a suitable metal core having a melting point higher than 1000 C. such as nickel, nlckel silicon, platinum or the like. After this metal has been thoroughly cleaned, it is given a thin in the form of graphite, or the more heavy deposit commonly known as soot, I prefer, however, to use the graphitizing process,

The filament is then given a coating of barium, strontium, or calcium oxide, either alone or in combination with one another.

' This combination is then raised in temperature sufficiently so as to form the carbides of the metals used in the coating. The carbides are better emitters than the oxides. I

have produced the carbides by another method in accordance with which I have first graphitized the core metal, then added a coating of the oxides or carbonates of the emitter metals to be employed and then added another coat of graphite. This combination is then mounted in the device where it is to be used and a voltage applied thereto during the pumping stage. This voltagemust be sufiicient so that the filament is raised to incandescence. This procedure will change the oxides or carbonates of the emitter metals to carbides, no matter in which form they have been applied. I

The ability of these cathodes to withstand positive ion bombardment is of exceptional value in connection with positive column tubes where the positive ion bombardment is of great magnitude.

From what has becnthus described, the nature ofmy invention will be readily clear to those skilled in the art and it will also be clear that modifications may be made withcoating of carbon either Application'filed. September 10, 1928. Serial No. 305,122.

put departing from the spirit of my invenion.

Having thus described one form which my invention may take, what I claim as new and desire to secure by Letters Patent is:

1. A metallic cathode coated with an emitter and having an outer thin surface layer of finely divided carbon.

2. A metallic cathode having a thin layer of finely divided carbon, a surrounding thin layer of an emitter and a coating of finely divided carbon. 7

3. The process of forming a cathode which consists in coating a metallic base with a finely divided carbon and with an emitter oxide 7 and then heating the combination to a temperature sufliciently large to change the oxide to a carbide.

4. A metallic cathode coated with an alkaline earth emitter and having an outer thin surface layer of finely divided carbon.

5. A metallic cathode having a thin layer of finely divided carbon, a surrounding thin layer of an alkaline earth emitter and a coating of finely divided carbon.

6. An electrode for gaseous conduction devices consisting of a base metal having barium carbide thereon.

7. An electrode for gaseous conduction devices consisting of a base metal having a coating thereon including a carbide of an alkaline earth metal.

8. A method of making an electrode for gaseousronduction devices which consists in coating a base metal with an oxide of an alkaline earth metal and heating said electrode in the presence of carbon whereby to at Least partially convert the coating to a car:

9. A cathode for positive column gaseous conduction tubes having a surface including a carbide of an alkaline earth metal.

10. An electrode for positive column gaseous conduction tubes consisting of a nickel base having'a discharge surface provided with a compound coating including a carbide of an alkaline earth metal.

In witness whereof, I hereunto subscribe my name this 3rd day of August, A. D. 1928.

RICHARD E. MIESSE. 

